Figure 5. Effect of several CAs and their conserved Glu mutants on NBCe1‐B activity .

A—C, the effects of CA12 and CA12(E143K) (A), CA4 and CA4(E138K) (B) and CA7 and CA7(E118K) on NBCe1‐B activity. HeLa cells transfected with the indicated plasmids and in Hepes‐buffered solutions were exposed to Na⁺‐free, HCO₃ ⁻‐buffered solutions to stably acidify the cytosol. The solutions also included 10 μm of the Na⁺–H⁺ exchangers inhibitor EIPA to inhibit all Na⁺–H⁺ exchangers. The Na⁺‐dependent HCO₃ ⁻ influx was initiated by exposing the acidified cells to a HCO₃ ⁻‐buffered solutions containing 10 μm EIPA and 140 mm Na⁺. The times of addition of external Na⁺ were aligned to facilitated comparison between experiments. The traces are the means ± SEM of number of experiments indicated in the columns under each condition. D, the means ± SEM of NBCe1‐B rates obtained from the initial slops of the pH_i increase on re‐addition of Na⁺ in the presence of HCO₃ ⁻ and of EIPA. The rates were normalized to the rate measured with NBCe1‐B alone. * denotes p < 0.05 and # denotes p < 0.01 with respect to NBCe1‐B alone. E and F, the means ± SEM traces (E) and rates (F) of slc26a6‐mediated Cl⁻–HCO₃ ⁻ exchange are not affected by CA12 and CA12(E143K) in transfected HEK cells. The numbers in the columns in D and F indicate the number of experiments obtained from at least 4 separate transfections.